Insulin-dependent Diabetes Mellitus Subjects Research Articles

Prolactin and β-endorphin responses to hypoglycemia are reduced in well-controlled insulin-dependent diabetes mellitus

Several pituitary hormones, including corticotropin (ACTH), growth hormone (GH), prolactin, and β-endorphin (but not thyrotropin, follicle-stimulating hormone, or luteinizing hormone), are released in response to hypoglycemia in normal subjects. In patients with insulin-dependent diabetes mellitus (IDDM), the degree of glycemic control is known to alter ACTH and GH responses to hypoglycemia. The current study was performed to examine the effect of glycemic control on prolactin and β-endorphin responses to hypoglycemia in subjects with IDDM. We performed 3-hour stepped hypoglycemic-hyperinsulinemic clamp studies (12 pmol/kg/min) during which plasma glucose was decreased from 5.0 mmol/L to 2.2 mmol/L in steps of 0.6 mmol/L every 30 minutes in 20 subjects with uncomplicated IDDM (12 males and eight females; age, 26 ± 2 years; IDDM duration, 10 ± 1 years; body mass index, 23.6 ± 0.6 kg/m 2) and 10 healthy subjects (five males and five females aged 30 ± 1 years). The 10 diabetic subjects in good glycemic control (mean hemoglobin A 1 [HbA 1], 7.5% ± 0.3%; normal range, 5.4% to 7.4%) were compared with the 10 poorly controlled patients (mean HbA 1, 12.6% ± 0.5%; P < 0.001 v well-controlled diabetic group). During hypoglycemia, prolactin levels in the well-controlled diabetic group did not change (7 ± 1 μg/L at plasma glucose 5.0 mmol/L to 9 ± 2 μg/L at plasma glucose 2.2 mmol/L), whereas prolactin levels increased markedly in the poorly controlled diabetic group (7 ± 2 μg/L to 44 ± 17 μg/L) and healthy volunteers (12 ± 2 μg/L to 60 ± 19 μg/L, P < .05 between IDDM groups). The plasma glucose threshold required for stimulation of prolactin secretion was 2.2 ± 0.1 mmol/L in well-controlled IDDM, 3.0 ± 0.4 mmol/L in poorly controlled IDDM, and 2.4 ± 0.1 mmol/L in healthy subjects ( P < .05 between IDDM groups). Responses in males and females were similar. The increase in β-endorphin levels was also attenuated in well-controlled IDDM patients (4 ± 1 pmol/L at plasma glucose 5.0 mmol/L to 11 ± 4 pmol/L at plasma glucose 2.2 mmol/L) versus poorly controlled IDDM patients (5 ± 1 pmol/L to 26 ± 7 pmol/L) and healthy subjects (8 ± 1 pmol/L to 56 ± 13 pmol/L). The plasma glucose threshold required for stimulation of β-endorphin release was again lower in well-controlled IDDM versus poorly controlled IDDM patients (2.2 ± 0.1 v 3.0 ± 0.3 mmol/L) and healthy subjects (2.5 ± 0.4 mmol/L, P < .05 between IDDM groups). In conclusion, prolactin and β-endorphin responses to a standardized hypoglycemic stimulus (plasma glucose, 2.2 mmol/L) are reduced and plasma glucose levels required to stimulate release of prolactin and β-endorphin are lower in well-controlled IDDM compared with poorly controlled IDDM and healthy subjects. Thus, stress hormones not previously considered to have a primary role in plasma glucose recovery from hypoglycemia are affected by glycemic control, suggesting a more generalized alteration of hypothalamic-pituitary responses to hypoglycemia in IDDM patients with strict glycemic control.

Cloning and Characterization of Islet Cell Antigen-related Protein-tyrosine Phosphatase (PTP), a Novel Receptor-like PTP and Autoantigen in Insulin-dependent Diabetes

Cloning of the cDNA encoding a novel human protein- tyrosine phosphatase (PTP) called islet cell antigen-related PTP (IAR) predicts a receptor-like molecule with an extracellular domain of 614 amino acids containing a hydrophobic signal peptide, one potential N-glycosylation site, and an RGDS peptide which is a possible adhesive recognition sequence. The 376-amino acid intracellular region contains a single catalytic domain. Recombinant IAR polypeptide has phosphatase activity. Northern blot analysis shows tissue-specific expression of two IAR transcripts of 5.5 and 3. 7 kilobases, which are most abundant in brain and pancreas. The IAR PTP is homologous in its intracellular region to IA-2, a putative PTP that is an insulin-dependent diabetes mellitus (IDDM) autoantigen. IAR is also reactive with IDDM patient sera. IAR and IA-2 may distinguish different populations of IDDM autoantibodies since they identify overlapping but nonidentical sets of IDDM patients. Thus IAR is likely to be an islet cell antigen useful in the preclinical screening of individuals for risk of IDDM.

Insulin treatment normalizes reduced free insulin-like growth factor-I concentrations in diabetic children.

We have recently demonstrated multiple aberrations in the GH-IGF axis in the sera of children with untreated insulin-dependent diabetes mellitus (IDDM) which were restored after insulin replacement. However, the net result of these alterations in the IGF system on the concentrations of free/biologically available IGF-I in the serum have not been examined directly in diabetic children. In the present study, the effect of diabetes and subsequent insulin replacement on the circulating free IGF-I concentrations are assessed. Fasting venous serum samples were obtained longitudinally, before and at various times after the initiation of insulin treatment in untreated diabetic subjects. Ten prepubertal, aged (mean +/- SEM) 6.3 +/- 1.0 years, and six adolescent, aged 12.7 +/- 1.1 years, subjects with newly diagnosed and untreated IDDM, and age and pubertal status-matched control children and adolescents were recruited. The serum samples were collected before initiating insulin treatment and 12-24 h, 1 week, and 1 month thereafter in subjects with IDDM. Insulin doses ranged from 0.5 to 1.2 U/kg/day. Free IGF-I concentration was assayed by a recently developed two-site immunoradiometric assay. Total IGF-I was measured by radioimmunoassay after acid-ethanol extraction of binding proteins. Differences in free and total IGF-I concentrations in IDDM subjects before and during insulin treatment were analysed by repeated measures analysis of variance followed by pairwise multiple comparisons test. In seven subjects with IDDM, where serum IGFBP-1 and IGFBP-3 concentrations, and IGFBP-3 protease activity had also been measured in a previous study, the relationship between these variables and circulating free IGF-I concentrations were examined by linear regression analysis. Free IGF-I concentrations in prepubertal subjects with IDDM were 0.9 +/- 0.2, 1.5 +/- 0.3, 1.6 +/- 0.3 and 2.5 +/- 0.4 micrograms/l before, 1 day, 1 week and 1 month after insulin treatment, respectively. Free IGF-I concentrations of control prepubertal children were 2.6 +/- 0.5 micrograms/l. Pubertal subjects had higher free IGF-I concentrations than prepubertal subjects but demonstrated a similar type of pattern; before insulin 2.3 +/- 1.1, 1 day 3.8 +/- 1.3, 1 week 3.7 +/- 0.6, 1 month 6.5 +/- 1.5 vs pubertal controls 7.7 +/- 2.0 micrograms/l. Total IGF-I concentrations were also reduced in untreated diabetic subjects and showed a slower pattern of normalization than free IGF-I concentrations. Free IGF-I concentrations correlated positively with total IGF-I and negatively with IGFBP-1 concentrations. There was no significant correlation between free IGF-I and either serum IGFBP-3 concentrations or IGFBP-3 protease activity. Alterations in the IGF system during untreated IDDM lead to a reduction in circulating free IGF-I concentrations which is restored progressively during insulin treatment. An increase in free IGF-I precedes that of total IGF-I suggesting that the former is a more sensitive indicator of the metabolic status. An inverse correlation between free IGF-I and IGFBP-1 supports the hypothesis that IGFBP-1 plays an important role in the acute modulation of free IGF-I levels.

Effects of insulin and lipid emulsion on renal haemodynamics and renal sodium handling in IDDM patients.

To evaluate the role of insulin and hypertriglyceridaemia in the regulation of renal haemodynamics and sodium handling in insulin-dependent diabetes mellitus (IDDM), 11 IDDM patients without microalbuminuria and 13 weight-, age-, protein intake- and sex-matched healthy control subjects were studied. Clearances of inulin (Cin), para-amino-hippuric acid (CPAH), sodium (CNa), and lithium (CLi) were measured in four 60-min clearance periods (periods I, II, III and IV) during isoinsulinaemia with lipid emulsion infusion (study 1), a hyperinsulinaemic isoglycaemic clamp with Intralipid infusion (study 2), and during time-controlled isoinsulinaemia (study 3). We found that Cin, CPAH and filtration fraction were comparable in IDDM and control subjects, whereas CNa was decreased in diabetic subjects (2.01 +/- 1.11 vs 3.03 +/- 1.32 ml/min; p < 0.05) due to elevations of proximal tubular fractional and absolute reabsorptions of sodium (p < 0.05). Insulin infusion did not affect Cin, increased CPAH (p < 0.05) and, consequently, lowered the filtration fraction (p < 0.01) in both groups. While acute hyperinsulinaemia resulted in increases in distal tubular fractional and absolute reabsorptions of sodium (p < 0.01) contributing to a fall in CNa (p < 0.01) in control subjects, in diabetic subjects the sodium-retaining effect of insulin was not significant. The lipid emulsion did not alter any of the estimated parameters. We conclude that IDDM without microalbuminuria is associated with a tendency to sodium retention which is not aggravated by insulin when compared to control subjects. Acutely induced hypertriglyceridaemia does not alter renal haemodynamics or renal sodium handling.

Increased lipid oxidation but normal muscle glycogen response to epinephrine in humans with IDDM.

The effects of physiological increments in epinephrine and insulin on glucose production (GP), skeletal muscle glycogen metabolism, and substrate oxidation were studied in eight insulin-dependent diabetes mellitus (IDDM) and nine control subjects. Epinephrine was coinfused for the final 120 min of a 240-min euglycemic, hyperinsulinemic clamp. In both groups, insulin increased glucose uptake, glycogen synthesis, and whole body carbohydrate (CHO) oxidation and inhibited GP (by 70-80%) and lipid oxidation (by approximately 50%), whereas epinephrine antagonized the effect of insulin on glucose uptake and glycogen synthesis. In contrast, GP increased in IDDM subjects (P < 0.02) but remained suppressed by insulin in controls. CHO oxidation fell (1.37 +/- 0.25 vs. 2.08 +/- 0.32 mg.kg-1.min-1) and lipid oxidation increased to baseline in IDDM subjects, with increments in plasma free fatty acids (FFA) and glycerol. In contrast, in controls, plasma FFA and glycerol remained suppressed and lipid oxidation decreased further with epinephrine (P < 0.005). Epinephrine completely reversed insulin's activation of muscle glycogen synthase in both groups. Thus, during hyperinsulinemia, the hepatic response to epinephrine in IDDM subjects may be dependent on activation of lipid oxidation. Skeletal muscle glycogen metabolism is exquisitely sensitive to epinephrine despite the presence of hyperinsulinemia.

Postprandial changes in high-density lipoprotein composition and subfraction distribution are not altered in patients with insulin-dependent diabetes mellitus

A detailed analysis of postprandial changes in the size, density, composition, and relative proportion of the major high-density lipoprotein (HDL) subfractions, HDL 2 and HDL 3, was performed in seven normolipidemic patients with insulin-dependent diabetes mellitus (IDDM) in moderate glycemic control and seven age-, sex-, and weight-matched healthy nondiabetic controls. IDDM subjects received an overnight insulin infusion to maintain euglycemia, with an incremental increase in the insulin infusion rate at the time of the test meal (containing 60 g fat/m 2). Samples for detailed analysis of HDL by gradient density ultracentrifugation and nondenaturing gradient gel electrophoresis (GGE) were collected at 0, 4, 8, and 12 hours after the test meal. The composition of HDL, HDL 2, and HDL 3 was significantly altered in the postprandial state in IDDM subjects and controls with an increase in triglyceride content at 4 to 8 hours and a reciprocal decrease in cholesteryl ester, reflecting exchange of lipid constituents of HDL with triglyceride (TG)-rich lipoproteins. In addition, the phospholipid content of the particles increased at 8 hours after the meal. Peak density of HDL 2 and HDL 3 decreased slightly at 4 to 8 hours, reaching significance only in controls at 8 hours ( P < .05), whereas the mean radius size of these subfractions did not change significantly. In controls and IDDM subjects, the ratio of HDL 3 to HDL 2 at 8 to 12 hours increased significantly ( P < .005). Significant differences in the composition, size, density, or subfraction distribution of HDL between subjects with IDDM and controls were not observed following ingestion of the lipid-rich meal. We conclude from these data that in patients with IDDM in moderate glycemic control, there do not appear to be any significant gross abnormalities in postprandial HDL metabolism with respect to the size, density, or compositional changes of HDL particles.

Circadian control of heart rate in young insulin-dependent diabetes mellitus patients

Our objective was to determine whether young insulin-dependent diabetes mellitus (IDDM) patients without complications have abnormal circadian patterns of sympathetic or parasympathetic control of heart rate. Twenty-four-hour electrocardiographic recordings in 26 IDDM patients without complications and 27 control subjects were obtained. Patients were in good health and participated in their usual daily activities. Power spectral analysis was performed to determine the amount of heart rate variability due to all (0.01-1.0 Hz), low (0.04-0.15 Hz), and high (0.15-0.40 Hz) frequency input signals hourly and throughout the entire 24-h period. Overall 24-h heart rate power did not differ between control and IDDM subjects. In IDDM subjects high-frequency power decreased with increasing diabetes duration ( r= −0.49, p = 0.013). A significant difference in circadian variation of heart rate power was only found for low frequency power ( p = 0.014). These results demonstrate that young IDDM subjects without diabetic complications have normal or near normal parasympathetic and sympathetic circadian patterns of heart rate control.

Socioeconomic and behavioural risk factors for mortality of individuals with IDDM in Japan: population-based case-control study. Diabetes Epidemiology Research International (DERI) US-Japan Mortality Study Group.

The aim of this population-based, one-to-one matched-pair case-control study was to evaluate the factors concerning the markedly increased risk for dying among Japanese subjects with insulin-dependent diabetes mellitus (IDDM) from a social and behavioural perspective. The study was based on the population-based cohort of IDDM subjects in the Diabetes Epidemiology Research International Mortality Study. We studied 90 cases who died and 90 living control subjects, selected from the rest of the cohort, who were matched for sex, birth year, year of diagnosis and duration of diabetes. Socioeconomic and behavioural status were surveyed through a questionnaire. Conditional logistic regression analyses based on 55 respondent pairs revealed that the better educated patients (year of completing education: odds ratio = 0.66) who kept the same physician (number of times a patient changed physician: odds ratio = 2.77) and who attended a clinic specializing in diabetes (attendance at university hospital clinic: odds ratio = 0.18) injecting insulin several times a day (number of injections, odds ratio = 0.31) and more frequently attending the clinic (> or = 12 times per year, odds ratio = 0.23) were at substantially lower risk of death. The results begin to profile the patients with the highest risk of dying who could be identified earlier and undergo intervention treatment.

Angiotensinogen polymorphism M235T, hypertension, and nephropathy in insulin-dependent diabetes.

The allele 235T (a threonine in place of a methionine at position 235) of angiotensinogen has been found to be associated with a predisposition to essential hypertension. We investigated whether this allele also confers increased susceptibility to nephropathy in patients with insulin-dependent diabetes mellitus (IDDM). A group of 380 patients who had had IDDM for 15 to 20 years were genotyped at the angiotensinogen 235 locus. Included were 75 patients with normoalbuminuria (albumin excretion rate < 30 micrograms/min), two series of patients with microalbuminuria (n = 30 and n = 136), and two series with overt proteinuria (n = 41 and n = 98). Allele 235T frequency was higher among cases with microalbuminuria (0.41 in the two series combined) or overt proteinuria (0.40) than in the normoalbuminuria group (0.36). However, this difference was not statistically significant with this sample size (chi 2 = 1.2, P = NS with 2 df). Under a recessive model, allele 235T homozygotes had a 1.6-fold risk of developing nephropathy relative to carriers of other genotypes, but this value was not significantly different from 1(95% CI = 0.8 to 3.5). The strength of the association did not improve after stratification by degree of glycemic control. With respect to the hypertension in these IDDM patients, no association with allele 235T was found. Allele 235T frequencies in normotensive and hypertensive individuals were 0.363 and 0.353, respectively, among normoalbuminuric IDDM individuals (chi 2 = 0.01, P = NS) and 0.411 and 0.414 among microalbuminuric IDDM subjects (chi 2 = 0.0, P = NS). We conclude that the angiotensinogen polymorphism M235T might influence susceptibility to nephropathy in insulin-dependent diabetes, but its effect, if any, is rather small and independent of hypertension.

VEP and ERP abnormalities in children and adolescents with prepubertal onset of insulin-dependent diabetes mellitus.

Visual evoked sensory (VEP) and event-related potentials (ERP) were assessed in 29 adolescents with insulin-dependent diabetes mellitus (IDDM) and in 29 controls matched for age and gender. Data were compared with clinical and psychometric measures, age at onset, duration of disease, and metabolic control. Analysis revealed no latency differences for the first cortical VEP component (P50) but a steadily increasing latency delay for subsequent VEP (N80, P100, N150, P200) and ERP components (P300) in the IDDM group compared to healthy controls. IDDM subjects showed highly significant latency prolongations (p < 0.001) for P100, N150 and P200 and P300 compared with healthy controls. A pathological VEP/ERP latency delay of more than 3 SD above the reference value range was observed in 21 IDDM patients (72.4%). Psychometric outcome measures in IDDM subjects showed no significant performance deficits on the Raven SPMs relative to non-diabetic controls. In contrast to VEP and ERP anomalies, which were highly interrelated, there was no tendency for neurophysiological and psychometric abnormalities to be contemporarily present. Neither electrophysiological nor psychometric measures were correlated with age at onset, IDDM duration, quality of metabolic control, or the presence of peripheral neuropathy. These findings give evidence that 1) higher cognitive functions are frequently affected in adolescents even with prepubertal IDDM onset, 2) neurophysiological ERP analysis seems to detect minor neurocognitive restrictions, presently not affecting psychometric outcome, 3) altered neurophysiological parameters were present in more than 70% of IDDM subjects studied, and 4) functional CNS disturbances affecting neurocognition are apparently not correlated with metabolic parameters previously thought to be important predictors of CNS outcome, suggesting the presence of multifactorial influences affecting neurocognition in IDDM subjects.

Distribution of HLA-DQA1 and -DQB1 alleles and DQA1-DQB1 genotypes among Senegalese patients with insulin-dependent diabetes mellitus.

Transracial analysis is one method for distinguishing primary associations between insulin-dependent diabetes mellitus (IDDM) and HLA II alleles from those related to linkage disequilibrium. Black people have different DR-DQ relationships from other races and are a useful group to investigate HLA-D regions associated with IDDM. In this study, we compared the frequencies of HLA-DQA1 and DQB1 alleles in Senegalese IDDM and control subjects. DQA1*0301 was positively associated with insulin-dependent diabetes mellitus (p < 10(-9), OR 5.21), as were DQB1*0201 and *0302 (p < 10(-7) OR = 3.55, p < 10(-3) OR = 3.20, respectively). The positive associations with DQA1*0301, DQB1*0201 and DQB1*0302 are consistent with all racial groups investigated. However, taken together, the data in Senegalese population show that susceptibility and resistance to IDDM are associated both with particular haplotypes and DQA1-DQB1 heterodimers.

Evidence for a hypothalamic-pituitary versus adrenal cortical effect of glycemic control on counterregulatory hormone responses to hypoglycemia in insulin-dependent diabetes mellitus.

The epinephrine and cortisol responses to hypoglycemia are reduced in insulin-dependent diabetes mellitus (IDDM) patients in strict glycemic control. However, it is not known whether these abnormalities are mediated at a central (hypothalamic-pituitary) or peripheral (adrenal) level. To examine this question, we measured counterregulatory hormone secretion during a 3-h hypoglycemic hyperinsulinemic clamp (12 pmol/kg.min) that lowered glucose from 5.0 to 2.2 mmol/L in steps of 0.55 mmol/L every 30 min in 13 well controlled IDDM subjects (hemoglobin A1, 7.8 +/- 0.2%), 14 poorly controlled IDDM subjects (hemoglobin A1, 12.3 +/- 1.5%), and 20 healthy volunteers. Basal levels of ACTH, cortisol, and epinephrine were similar in all 3 groups before hypoglycemia. At the nadir glucose level (2.2 mmol/L), ACTH, cortisol, and epinephrine levels were significantly lower in well controlled IDDM compared to healthy controls, and the glucose levels required for significant secretion of ACTH, cortisol, and epinephrine also were lower in well controlled IDDM compared to those in both poorly controlled IDDM and healthy volunteers (P < 0.05). During hypoglycemia, ACTH levels were significantly correlated with cortisol levels (r = 0.43; P < 0.05). Because adrenomedullary epinephrine synthesis is partially dependent on adequate adrenocortical function, we also determined whether the blunted epinephrine response might result from the reduced cortisol secretion. Eleven of the control subjects underwent a second identical insulin clamp study during which metyrapone was administered to produce adrenal cortical blockade. Despite higher basal ACTH levels after metyrapone and sustained elevations in ACTH during hypoglycemia, the cortisol response was abolished during metyrapone treatment, indicating effective blockade. However, epinephrine responses did not differ during hypoglycemia with or without metyrapone treatment. We conclude that 1) ACTH, cortisol, and epinephrine responses during hypoglycemia are reduced in IDDM patients in strict glycemic control; 2) the lower cortisol response is correlated with reduced ACTH levels; and 3) in healthy subjects, the cortisol response to hypoglycemia is abolished by adrenocortical blockade with metyrapone, whereas the epinephrine response to hypoglycemia remains intact. These data suggest that central adaptations in hypothalamic-pituitary responses to hypoglycemia rather than alterations in adrenal gland function per se underlie the reduced counterregulatory responses seen in IDDM subjects in strict glycemic control.

Changes in high density lipoprotein subfraction lipids during neutral lipid transfer in healthy subjects and in patients with insulin‐dependent diabetes mellitus

While it is known that the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to the apo B-containing lipoproteins is increased in patients with diabetes, the extent to which the various lipoprotein fractions engage in neutral lipid exchange and the magnitude to which triglyceride (TG) is translocated is not known. To examine in greater detail neutral lipid net mass transfer in diabetes, the HDL subfractions and the apo B-containing lipoproteins were separated, and the net mass transfer of CE and TG was compared to that of control subjects. In both groups, bidirectional transfer of CE from HDL3 to very low density lipoprotein (VLDL) + low density lipoprotein (LDL) and of TG from VLDL + LDL to HDL3, took place, but this process was significantly greater (P < .01) in insulin-dependent diabetes mellitus (IDDM). In contrast, CE and TG accumulated in HDL2 to a similar degree in normal and IDDM subjects. In recombination experiments with each of the apo B-containing lipoproteins, IDDM VLDL had a greater capacity to facilitate the exchange of core lipids from both IDDM and control HDL3: on the other hand, LDL from IDDM and control subjects both donated TG and CE to HDL2 and affected little change in HDL3. These findings indicate that all the major plasma fractions normally participate in the trafficking of CE and TG among the lipoproteins during neutral lipid transfer and show that the principal perturbation in cholesteryl ester transfer in IDDM involves altered interaction between VLDL and the HDL3 subfraction.

Effects of dietary protein restriction on regional amino acid metabolism in insulin-dependent diabetes mellitus.

We studied subjects with insulin-dependent diabetes mellitus (IDDM) and controls by administering primed continuous infusions of L-[1-13C,15N)]leucine and L-[2,3-13C2]alanine to measure whole body and forearm metabolism of these amino acids during ample protein intake and again after 4 wk of moderately restricted protein intake. Decreased rates of whole body protein degradation, leucine transamination, leucine oxidation, and increased forearm alanine release produced by dietary protein restriction occurred equivalently in IDDM subjects under short-term tightly managed glycemia and in controls. Dietary protein restriction did not affect whole body alanine appearance or forearm leucine appearance, disposal, or balance in IDDM subjects or controls. IDDM subjects differed from controls only in that normal forearm leucine balance was maintained at higher rates of leucine appearance and disposal. We conclude that IDDM subjects adapt normally to dietary protein restriction. Undernutrition during moderate protein deprivation in these patients likely occurs during episodes of poor glycemic control.

HLA-DRB1*0401 is associated with susceptibility to insulin-dependent diabetes mellitus independently of the DQB1 locus.

The distribution of DRB1*04 alleles and DRB1/DQB1 haplotypes was analysed in 57 DR4+ caucasoid subjects with insulin-dependent diabetes mellitus (IDDM) and 96 DR4+ healthy controls selected on the basis of DR serology, and the findings were analysed in relation to age at diagnosis of IDDM. DNA samples were amplified using specific DR and DQ primers and hybridized with sequence-specific oligonucleotide probes. A significantly increased combined frequency of DRB1*0401 and 0402 was observed in IDDM subjects aged < or = 12 years at diagnosis (allele frequency 88.4% compared with 62.0% in controls, P < 0.025). There was a non-significant increase in DRB1*0401 and 0402 in IDDM subjects < or = 12 years when compared with IDDM subjects > 12 years (P < 0.1). DRB1*0404 was decreased in the total IDDM subject group compared with controls (4.8% vs. 19.0%, P < 0.025) but did not reach statistical significance in the individual age at diagnosis groups. In contrast, the frequency of DQB1*0302 was increased uniformly across both ages at diagnosis groups. In controls DRB1*0401 occurred in haplotype association with DQB1*0301 in a significantly greater frequency than with DQB1*0302. However, 95.0% of DRB1*0401 IDDM subjects were DQB1*0302. DRB1*0404, which was decreased in frequency in IDDM subjects, occurred in association significantly more frequently with DQB1*0302 in controls. These results imply that DRB1 and DQB1 have independent roles as HLA susceptibility genes in IDDM. DQB1 may have a permissive role whereas DRB1 could influence the rate at which underlying disease progresses to clinical IDDM.

Sympathetic vasoconstrictive responses to high- and low-sodium diets in diabetic and normal subjects.

Uncomplicated insulin-dependent diabetes mellitus (IDDM) is associated with a suppressed reflex response to sympathetic nervous system (SNS) stimulation and an enhanced pressor response to catecholamines. This study examined the SNS in subjects with IDDM (duration < 5 yr, n = 9) to determine the responsible mechanism within the cardiopulmonary baroreflex arc and the role played by extracellular fluid volume (ECFV) expansion. The reflex arc was tested by examining the plasma norepinephrine (PNE) and forearm vascular (FVR) responses to 60 min of cardiopulmonary baroreceptor unloading by lower body negative pressure (LBNP) at -15 mmHg. The effector limb was tested by measuring the PNE, FVR, and mean arterial pressure (MAP) response to the cold pressor test (CPT). The postganglionic neuroeffector junction was tested by measuring the venoconstrictive response to local norepinephrine infusion. ECFV was varied by altering dietary sodium. In IDDM subjects on a 250 mmol sodium diet, PNE and FVR responses to LBNP (delta PNE = 0.15 +/- 0.05; delta FVR = 4.3 +/- 1.2) were attenuated compared with controls (delta PNE = 0.36 +/- 0.23; delta FVR = 11.56 +/- 2.72). MAP and FVR responses to the CPT were intact (delta MAP = 9.74 +/- 1.9; delta FVR = 7.02 +/- 3.11) compared with controls (delta MAP = 10.74 +/- 2.69; delta FVR = 8.26 +/- 2.94), but the PNE response was attenuated. The peripheral vasculature was hyperresponsive to norepinephrine infusion in IDDM subjects [mean effective dose (ED50) = 57 +/- 10 ng/min] compared with controls (ED50 = 133 +/- 30 ng/min). Sodium restriction (20 mmol/day) normalized the FVR response to LBNP and the venous response to norepinephrine infusion. The PNE response both to LBNP and the CPT remained attenuated.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated plasma ceruloplasmin in insulin-dependent diabetes mellitus: Evidence for increased oxidative stress as a variable complication

Cerulopiasmin (Cp) is an acute-phase—responsive oxidase enzyme. Prior reports suggest that Cp is increased in diabetes mellitus, perhaps reflecting greater oxidant stress. However, the situation in insulin-dependent diabetes mellitus (IDDM) per se remains unclear. Furthermore, vitamin C can interfere with one indirect assay for Cp, and vitamin C metabolism is altered in IDDM. We measured Cp levels by both a direct radial immunodiffusion (RID) assay and an indirect oxidase assay in 10 subjects with IDDM and 10 nondiabetics, both at baseline and after 30 days of vitamin C supplementation (100 or 600 mg daily, five subjects per group). Plasma copper level was measured independently also. Our data show that circulating levels of Cp are significantly increased in IDDM subjects as a group, and specifically that Cp is abnormally high in a subset of IDDM individuals. Vitamin C supplementation at either dose interfered with the oxidase assay for Cp in both groups, but vitamin C did not alter the RID assay. The observed increase in plasma copper suggests that circulating holo-Cp is increased. The finding of increased Cp in some individuals with IDDM supports the hypothesis of increased oxidant stress as a variable factor in the spectrum of chronic complications in diabetes. Measurements of Cp level by the oxidase assay must be considered unreliable for subjects taking vitamin C supplements of ≥100 mg/d.

Analysis of Families at Risk for Insulin-Dependent Diabetes Mellitus Reveals that HLA Antigens Influence Progression to Clinical Disease

Individuals at risk for insulin-dependent diabetes mellitus (IDDM), with an affected first-degree relative, can be identified by the presence of islet cell antibodies (ICA). ICA-positive relatives progress at variable rates to IDDM and identification of those at highest risk is a prerequisite for possible preventative treatment. Those who develop IDDM may exhibit less genetic heterogeneity than their ICA-positive or ICA-negative relatives. Specific human leucocyte antigen (HLA) genes predispose to IDDM but could also influence the rate of progression of preclinical disease. Therefore, by comparing HLA antigen frequencies between first-degree relatives, we sought to identify HLA genes that influence progression to IDDM. HLA antigen frequencies were compared in 68 IDDM, 53 ICA-positive, and 96 ICA-negative first-degree relatives from 40 Caucasoid families. Predictions were tested in a panel of 270 unrelated IDDM subjects. HLA typing was performed serologically (HLA class I and II) and by sequence-specific oligotyping (11th International Histocompatibility Workshop protocol) (HLA class II). ICA tests were measured by an internationally standardized indirect immunofluorescence assay. In general, known susceptibility class II HLA antigens increased in frequency and known protective class II HLA antigens decreased in frequency, from ICA-negative to ICA-positive to IDDM relatives. Thus, DR4 and DQ8 increased whereas DR2 and DQ6 decreased; DR3 and DQ2 increased from ICA-negative to ICA-positive relatives, but not further in IDDM relatives. The high-risk DR3, 4 phenotype increased across the three groups; DR4,X was unchanged, and DR3,X and DRX,X both decreased. The HLA class I antigen, A24, occurred more frequently in ICA-positive relatives who developed IDDM and, in 270 unrelated IDDM subjects, was associated with an earlier age at diagnosis of IDDM in those with the lower risk class II phenotypes DR4,4 and DR3,X. HLA-DR3 and DQ2 predispose to islet autoimmunity, but not development of clinical IDDM in the absence and DR4 and DQ8. DR4 and DQ8 predispose to the development of clinical IDDM in ICA-positive relatives, in combination with DR3-DQ2 and other haplotypes but not when homozygous. HLA-A24 is significantly associated with rapid progression to IDDM in ICA-positive relatives and with an earlier age at clinical diagnosis. Analysis of IDDM families reveals that HLA genes not only predispose to islet autoimmunity but influence progression to clinical disease. The findings have implications for identifying high-risk relatives as candidates for possible preventative therapy.

Section Review—Oncologic, Endocrine &amp; Metabolic: Potential Use of Vanadium Compounds in the Treatment of Diabetes Mellitus

Vanadium is a trace element of ubiquitous occurrence. Vanadium compounds have been shown to exert a variety of insulin-like effects both in vitro and in vivo. These effects include their ability to lower hyperglycaemia in animal models of type I, insulin-dependent diabetes mellitus (IDDM), and type II, non-insulin-dependent diabetes mellitus (NIDDM). Vanadium therapy also corrects several metabolic abnormalities associated with the diabetic state. Preliminary studies in human diabetic subjects have shown an improved insulin sensitivity in NIDDM and in some IDDM subjects. Thus, vanadium compounds, either alone or in combination with other agents, have the potential to serve as antidiabetic agents.

Reduced awareness of hypoglycemia in adults with IDDM. A prospective study of hypoglycemic frequency and associated symptoms.

To prospectively evaluate the frequency and severity of hypoglycemic episodes in IDDM subjects who declare themselves to have reduced awareness of hypoglycemia, to validate their self-designations in their natural environment, and to determine objectively the presence or absence of autonomic and neuroglycopenic symptoms associated with their low blood glucose (BG) levels. A total of 78 insulin-dependent diabetes mellitus (IDDM) subjects (mean age 38.3 +/- 9.2 years; duration of diabetes 19.3 +/- 10.4 years) completed two sets of assessments separated by 6 months. The assessments included reports of frequency and severity of low BG, symptoms associated with low BG, and a BG symptom/estimation trial using a hand-held computer (HHC). Diaries of hypoglycemic episodes were kept for the intervening 6 months. HbA1 levels were determined at each assessment. Of the subjects, 39 declared themselves as having reduced awareness of hypoglycemia (reduced-awareness subjects). There were no differences between these reduced-awareness subjects and aware subjects with regard to age, sex, disease duration, insulin dose, or HbA1. During the HHC trials, reduced-awareness subjects were significantly less accurate in detecting BG < 3.9 mmol/l (33.2 +/- 47 vs. 47.6 +/- 50% detection, P = 0.001) and had significantly fewer autonomic (0.41 +/- 0.82 vs. 1.08 +/- 1.22, P = 0.006, reduced-awareness vs. aware) and neuroglycopenic (0.44 +/- 0.85 vs. 1.18 +/- 1.32, P = 0.004, reduced-awareness vs. aware) symptoms per subject. Prospective diary records revealed that reduced-awareness subjects experienced more moderate (351 vs. 238, P = 0.026) and severe (50 vs. 17, P = 0.0062) hypoglycemic events. The second assessment results were similar to the first and verified the reliability of the data. IDDM subjects who believe they have reduced awareness of hypoglycemia are generally correct. They have a history of more moderate and severe hypoglycemia, are less accurate at detecting BG < 3.9 mmol/l, and prospectively experience more moderate and severe hypoglycemia than do aware subjects. Neither disease duration nor level of glucose control explains their reduced awareness of hypoglycemia. Reduced-awareness individuals may benefit from interventions designed to teach them to recognize all of their potential early warning symptoms.